A magnetoresistance effect magnetic head is a part used as a sensor to reproduce magnetic information recorded on a magnetic recording medium in a magnetic recording device of high recording density, primarily a hard disk, and largely governs the performance of magnetic recording technology.
Magnetic reproducing heads utilizing the magnetoresistance effect of a multilayer film having ferromagnetic metal layers laminated with a nonmagnetic intermediary layer in between, or so-called giant magnetoresistance effect (hereafter, GMR), or the like, have been used in recent years. The GMR head initially used was a CIP (current-in-plane) head, in which an electric signal is charged parallel within the film surface. To improve recording density, TMR (tunneling magnetoresistance effect) heads and a CPP-GMR (current perpendicular to plane-giant magnetoresistance effect) heads were developed, which appeared to be useful for obtaining high output by narrowing the track width and narrowing the gap. The TMR head has become the mainstream in magnetic reproducing heads today. The TMR head and the CPP-GMR head, unlike the conventional GMR head, greatly differ from CIP heads in that the sense current travels in a direction perpendicular to the planes of the sensor layers, rather than parallel.
Refining the effective track width of a magnetoresistive sensor and obtaining a high S/N ratio are required to respond to the demand in recent years for even higher density recording. Although there is a phenomenon of information being read in the width direction of reproduction tracks from an adjacent or nearby track, or so-called side reading, this phenomenon can be suppressed by forming a side shield structure of a soft magnetic material arranged to the left and right of the sensor.